Pakistani security officials at the scene of the Jamrud market bombing in the Khyber tribal area. Photograph: A Majeed/AFP/Getty Images

A car bomb exploded in a crowded market in Pakistan's troubled north-west tribal region, killing 17 people and wounding more than 40 others, officials said.

The bomb went off on Monday next to the women's waiting area of a bus stop near the office of one of the top political officials in the Khyber tribal area, said Hidayat Khan, a local government official. But it was unclear if the office was the target.

The 17 dead included five boys and two women, said Abdul Qudoos, a doctor at a local hospital in Jamrud town, where the attack occurred. At least 44 people were wounded, he said.

Local TV footage showed several badly damaged cars and shops in the market. Residents threw buckets of water on burning vehicles as rescue workers took the wounded to hospital.

The market was close to the office of the assistant political agent for Khyber, said Khan, who works in the office. Initial reports wrongly indicated the women's waiting area was for the political office, not the bus stop.

No group immediately claimed responsibility. Khyber is home to various Islamist militant groups, including the Pakistani Taliban, who have waged a bloody insurgency against the government for the past few years.

The army has carried out offensives against the Taliban in most parts of the tribal region, including Khyber, but militants continue to carry out regular attacks.

Also on Monday, gunmen killed a provincial government spokesman in south-west Pakistan in an apparent sectarian attack, and then shot dead two nearby policemen, officers said.

The attackers killed Khadim Hussain Noori in Quetta, the capital of Baluchistan province, said local police official Hamid Shakeel. Noori was the provincial spokesman and also a Shia Muslim.

As the gunmen sped away on a motorcycle, they killed two policemen and wounded a third, said Shakeel.

Baluchistan has seen a spike in sectarian killings in the past year as radical Sunni Muslims have targeted Shias, whom they consider heretics.

There has also been a decades-long insurgency by Baluch nationalists demanding greater autonomy and a larger share of the province's natural resources.